The sampling and testing of biological fluids such as urine for the presence of analytes provides important information regarding various health related maters, including pregnancy and conception.
For an example, current test devices use an immunoassay for determining pregnancy or conception. At the heart of the immunoassay is a reagent, such as an antibody, that specifically reacts with an analyte to form a reaction complex. The immunoassay also can include and one or more separate detection reagents that react with the reaction product to facilitate detection of the reaction complex. The reaction complex can usually be detected by the unaided eye. An immunoassay can produce qualitative or semi-quantitative results.
Current pregnancy test devices assay for hormones associated with pregnancy, such as, for example, chorionic gonadotropin. Normally, the presence of human chorionic gonadotropin in urine is an indicator that a woman may be pregnant. Such test devices obtain qualitative results indicating either the presence or absence of chorionic gonadotropin. Typically, a pregnancy immunoassay contains an antibody directed against chorionic gonadotropin and a separate detection antibody.
Conception test devices also assay for hormones associated with the ovarian cycle, such as, for example, luteinizing hormone. Luteinizing hormone is present normally in urine but its concentration increases markedly during ovulation, the time at which a women is most likely to conceive. The probability that a woman can conceive a child thus increases with increasing concentration of luteinizing hormone. Such test devices obtain semi-quantitative results regarding the relative concentration of luteinizing hormone in the urine. Typically, a conception immunoassay contains an antibody directed against luteinizing hormone and a separate detection antibody.
Current test devices use various sample collection and analytical methods to detect an analyte in urine. For example, in one method urine is collected in a container and a measured urine volume transferred to a solution containing the immunoassay. The reaction product is detected in the resulting solution or as applied to a solid support. However, this method requires that the urine volume be accurately measured to insure the reaction product is not so diluted that it cannot be easily detected. In many situations, such as at-home testing, accurate measurement of urine volume is difficult perform and undesirable. Moreover, urine collection in a container and transfer to a test device generally is undesirable because of sanitary concerns and the potential for contamination.
In another method, the urine is collected in a container and transferred to a test device having an absorbent material that conducts or "wicks" the urine via capillary attraction to the immunoassay on a membrane. Typically, such a membrane immunoassay or absorbent material contains an antibody directed against the antigen of interest conjugated with a dye agent and an antibody directed to the antigen immobilized on the membrane immunoassay at a position "upstream" from the dye conjugate antibody. As the urine flows through the membrane immunoassay, the dye conjugate antibody binds the antigen and flows to the immobilized antibody where an antibody "sandwich" reaction complex is formed. A second absorbent material is positioned upstream from the immobilized antibody and in fluid flow contact with the membrane immunoassay to draw urine through the membrane immunoassay and collect urine and unbound dye conjugate antibody. The immobilized antibody typically is bound to the membrane in a line across the membrane immunoassay which results in a positive reaction appearing as a line.
A casing, usually made of plastic, surrounds the membrane immunoassay and the absorbent material in a manner that allows urine to be added only to the absorbent material. The absorbent material controls the volume of urine that contacts the immunoassay because only urine conducted by the absorbent material contacts the membrane immunoassay. Therefore, the volume of urine added to the absorbent material need not be accurately measured so long as a sufficient amount is added to allow the reaction to occur. An opening or window on one side of the casing over the membrane immunoassay permits the result to be observed. However, the collection of urine in a container and its transfer to the test device are disadvantages of the method because of sanitary concerns and the potential for contamination.
In another method, the urine is collected directly from the urine stream into the test device. The in-stream test device contains an absorbent material that is attached to and projects outward from a casing surrounding the above-described membrane immunoassay. The casing is designed as a handle to facilitate inserting the absorbent material into the stream during urination. The absorbent material is rigid so as to prevent being deflected out of the stream and not collecting a sufficient amount of urine. As described above, the absorbent material controls the amount of urine that contacts the membrane immunoassay and an opening or window on the casing permits the result to be observed. After collecting the urine, a cap may be placed over the absorbent material to contain the residual urine on the absorbent material and facilitate handling.
A disadvantage of current test devices is the relatively high cost to manufacture and use these test devices. A principle reason the test devices are expensive to manufacture is that each test device requires the manufacture and assembly of many separate parts. For example, an in-stream test device typically contains an absorbent material, a membrane immunoassay, a desiccant, two or more casing parts and a window. Each of these parts must be separately manufactured and then assembled in each test device which results in a high manufacturing cost for each test device.
Current test devices are expensive to use because each test device can only be used once. Since the cost of each test device is relatively high, a user incurs significant expense when multiple tests are required. For example, a conception test often requires testing for luteinizing hormone once a day for five or more days to optimize the probability of conception. The high cost of current test devices is a disadvantage particularly in underdeveloped regions of the world where the need for such test devices is great but cost significantly limits their use.
Another limitation of current test devices is that the result obtained cannot be conveniently stored. For example, urine soaked absorbent material contains microorganisms and the growth of such microorganisms in the absorbent material prohibits storage of the test device. Moreover, the result cannot be easily removed from the test device for separate storage from the absorbent material.
Yet another limitation of current test devices utilizing an absorbent material is that the result can only be observed from one side of the device. The ability to observe the result from more than one side would facilitate use, especially for in-stream test devices.
There thus is a need for a test device that detects analytes in urine which is more economical to manufacture and use than current test devices. There also is a need for a test device that allows the result to be archived for storage. Further, there is a need for a test device that allows the result to be viewed from more than one side of the device. Finally, the test device should be simple enough to used by the lay individual outside of a medical facility or any location such that medically trained individuals are not required to use the device. For instance, pregnancy tests are often conducted by the patient in her own home. The present invention satisfies these needs and provides related advantages as well.